Minecraft.net has the link to the wrong issue.

In the bedrock changelog for the spring to life update https://feedback.minecraft.net/hc/en-us/articles/35256043330189-Minecraft-Bedrock-Edition-1-21-70-Spring-to-Life under the mobs category for bug fixes means an issue involving invisible mobs. The bug has a link to the bug tracker, but the link is for the wrong issue and instead links to an issue about a nether portal MCPE-188731.